Reduction and Cycloaddition of Heteroalkenes at Ga(I) Bisamide Center

Abstract

The reactivity of the complex [(dpp-bian)GaNa(DME)2] (1) (dpp-bian = 1,2-bis[(2,6-di-isopropylphenyl)imino]acenaphthene) towards isocyanates, benzophenone, diphenylketene, and 1,2-dibenzylidenehydrazine has been studied. Treatment of 1 with isocyanates led to derivatives of imidoformamide [(dpp-bian)Ga{C(=NPh)2}2–NPh][Na(DME)3] (2), biuret [(dpp-bian)Ga(NCy)2(CO)2NCy][Na(DME)] (3), or carbamic acids [(dpp-bian)GaN(Cy)C(O)O]2[Na(THF)(Et2O)] (4), [(dpp-bian)GaC(=NCy)N(Cy)C(O)O][Na(Py)3] (5). Treatment of 1 with 2 equiv. of Ph2CO resulted in gallium pinacolate [(dpp-bian)GaO(CPh2)2O][Na(Py)2] (9), while the reaction of 1 with 2 equiv. Ph2CCO gave divinyl ether derivative [(dpp-bian)Ga{C(=CPh2)O}2][Na(DME)3] (10). Complex 1 treated with 2 equiv. 1,2-dibenzylidenehydrazine underwent [1+2+2] cycloaddition to give C–C coupling product [(dpp-bian)Ga{N(NCHPh)}2(CHPh)2][Na(DME)3] (11). When complex 1 was sequentially treated with 1 equiv. of 1,2-dibenzylidenehydrazine and 1 equiv. of pyridine or pyridine-d5; it gave [1+2+2] cycloaddition product [(dpp-bian)GaN(NCHPh)C(Ph)CN][Na(DME)3] (12). Compounds 2–12 were characterized by NMR and IR spectroscopy, and their molecular structures were established by single-crystal X-ray diffraction analysis.